heard from the nfl. we've had some positive response from the players association. and a lot of encouragement from other scientists that this is interesting work. >> brown: just finally dr. small beyond sports and i guess this applies also to war injuries as well. what are the other implications of looking at the brain this way? you yourself do a lot of work in alzheimers so what's the link? >> i think the link is that we've got to protect our heads. whether it's from head trauma, whether it's from wear and tear from aging, whether it's stress, lack of exercise, overweight, obesity. there are so many physical problems that can wreak havoc on our brain health. we've really got to be careful of protecting our brains. >> brown: dr. gary small of ucla. thanks so much >> thank you. >> brown: you can find links to past newshour coverage on concussions and the health consequences on our home page. >> ifill: 40 years after it became legal, the debate over abortion rights has not gone away. according to a new "wa